Also am I wearing my cuff high enough?

Due to the arm's shape, all arms, and due to the cuff's geometry, it doesn't matter as long as you can get the cuff on and the Velcro to catch. If that happens, and it's not badly askew, or the Velcro keeps peeling itself away, then you're good. The machine goes to a certain pressure, an upper limit, and then bleeds off the air until it begins to detect the systolic pressure. That's your systolic, and it continues to bleed off air until it can't detect your diastolic pressure...those beats. Those are your numbers...period.

The cuff does have to be worn in a certain position, though....it matters. The literature will describe where to put the 'arrow', which way the arrow should face (usually toward the wrist), and there's a sign indicating where the sensor is. The sensor should be over the brachial artery. This means the spot where they say to place the sensor, or place the 'line'....whatever the instrument YOU have says is the sensing spot, at the base of the bicep muscle. Not near the elbow...not THAT base, but the bottom edge of the elongated muscle. If you do an arm flex, and feel along the bony are of your upper arm, just below that bunched up muscle...that's where the sensor should be.

You might take it with you to your next doctor's appointment and have the help

I would talk with your doctor about getting a larger blood pressure cough. They do have many different sizes and I think depending on your medical insurance they might be covered and you need to go to a medical store. As I have trouble because they keep wanting to use this very big one fat and cardiology told me an adult long for me, but I am sure you need the next size up.
I wish you the best because I don’t know where you live and you can check Amazon and see if they have a longer cough. I’ll talk to your doctor first.

If you have enough adipose padding that the device can't properly minipulate your artery at the elbow you might consider a wearable device or a wrist unit.

Great question, @ehdog. I particularly love it because of fantastic timing with my own nurse visit to review how I am taking my blood pressure (bp) at home.

Everyone is bringing up good thoughts to consider. My thoughts go to the root of why you are asking. My doctor recently recommended medication changes, wanted me to bring my home machine in and visit with a nurse for education and make sure my home readings are accurate. The nurse watched me put on the cuff and take my own bp. Then, she took a series of readings alternating between her machine and mine. She determined my machine is accurate, I know how to take my readings properly and helped me understand parameters as to when I would need to contact my doctor. Now I am all set to manage my bp and my doctor knows readings I pass on to her are reliable. I suspect this may eliminate the needs to see my doctor in the clinic should I notice changes.

I guess I give you details of my recent experience to add into the mix of the good recommendations you are reading from others, to encourage you to run your questions by your doctor, maybe request the same type of appointment. It is making things less stressful here because I know my doctor will find the readings I take as reliable and I know when to contact her.

Do you have a specific schedule, or reason you are monitoring your blood pressure? Do you have a range that is “safe” for you?

What brand is your unit? Looks like one of those Vital Track units which is pricey, but can be a PITA to use one-handed.

When I get my 24 hour monitoring the cuff is usually a sloppy fit, but they get a lot of good readings out of it.

BP cuffs typically come in 2 sizes adult regular and adult large. There are smaller ones for kids too. The adult large or x-large should work but they don’t usually come with the automatic cuffs. You need to buy it separately unfortunately.

My recent 24 hour check the fit was snug. Somehow it got knocked awry and during the reading it got so tight I knew it would wake me up. My arm was so sweaty and sticky I couldn't adjust it without loosening it. Don't know if had any effect, but I had a lot of good readings and all were high.

I have 2 different units where the cuff from one plugs into both base units, but the cuff from the other one does not plug into both base units.

I have since learned I was using the cuff wrong. It should be about 1.5 inches from your tendon. Try to feel your pulse in the vicinity of the tendon. If you can't feel it then the thingy in the cuff may not either. Would suggest using a wrist device which you can verify at your doc's office. I look for trends and not exact numbers/results. Yesterday mid-afternoon in the hand surgeon's office it was 100/64. I don't recall EVER having a legit reading that low.